An aligner-type orthodontic appliance has a polymeric shell that generally covers most or all of the teeth when worn. The appliances are often highly transparent and clear, to an extent that it may be difficult to detect that the appliance is being worn. Some or all of the tooth-receiving interior of the appliance is configured so that when worn, the walls of the appliance apply a force to an adjacent tooth or teeth that over time urges the tooth or teeth in a particular way to effect a movement of the tooth or teeth as part of an orthodontic treatment to reposition the teeth. The urging force is provided by the energy stored in a spring-like deformation of the appliance walls as the appliance is forced onto the teeth and into the position when the appliance is worn. It is the slow dissipation of this stored energy the triggers the underlying processes of tooth movement.
Aligner therapy often involves a series of progressive appliances to progressively reposition teeth. Each aligner may be used for a relatively short period of time, on the order of perhaps a few to several weeks. A new aligner is then applied that urges further movement of the teeth. In this sense, the series of appliances may be considered to be progressively biased. Additional aligners are used until the teeth have been urged to move a desired final positioning.
Such aligner-type appliances may be made by a variety of techniques, which may be performed in a commercial laboratory or on-site at an orthodontist office. One technique is by thermoforming over a model corresponding to a configuration for treatment of the patient's teeth, using a thermoforming machine such as the Biostar Thermoformer or other similar dental thermoforming device. Such thermoforming may be performed at commercial laboratories or on-site at orthodontists' offices. Appliances made by such thermoforming devices are sometimes referred to as “suck-down” appliances, reflecting the use of a vacuum to help form a heated sheet of polymeric material to the pattern of the model. A variety of polymeric materials have been used to make thermoformed appliances. Various blends of such polymers have been used to achieve different combinations of mechanical and optical properties.
One commercially available fabrication service for alignment-type appliances is known as the Invisalign® program. Invisalign® products are not made by a suck-down technique. The Invisalign® aligner fabrication process is technologically sophisticated and uses digitization of impressions and pictures of teeth and 3D computer imaging.
Aligner-type appliances are widely used in a variety of orthodontic situations, and there is a significant need for versatility in such appliances to meet a wide variety of treatment considerations.
For some orthodontic treatments involving the use of aligner-type shells, it is desirable to attach orthodontic components to the outside of the shell. One bonding adhesive that has been proposed for that purpose is the light-activated ClearLoc™ adhesive, which has been reported in a Material Safety Data Sheet to contain 50-55 percent polyurethane oligomer, 26-39 percent high boiling point (meth)acrylate, 15-26 percent aliphatic amide, 1-5 percent photoinitiator and 0.01 to 1 percent organic dye. Appliances with orthodontic components attached using the ClearLoc™ adhesive have had some limited success, but attached components do not uniformly display a level of bond strength or durability that may be desired in many of the wide variety of orthodontic situations, or other dental situations.
Although highly clear, transparent appliance shells are often desirable to “hide” the presence of the appliance, in some instances it would be desirable to have appliances that are not transparent, or not entirely transparent. For example, especially with younger orthodontic patients, adding colorful decoration to the appliance may make the appliance more desirable as personal ornamentation and may promote better compliance with an orthodontic treatment program. It has been proposed, for example, to esthetically enhance appliances by attaching decorative items to the appliance, for example dental decals, using the ClearLoc™ adhesive. However, decals are not ideal for customizing decoration to the particular patient and, as already noted, the ClearLoc™ adhesive has not satisfied bond strength and durability needs for a variety of situations.